docs: def create_unique_transfer_operation_id(src_ase, dst_ase):
          # type: (blobxfer.models.azure.StorageEntity,
          #        blobxfer.models.azure.StorageEntity) -> str
          """Create a unique transfer operation id
          :param blobxfer.models.azure.StorageEntity src_ase: src storage entity
          :param blobxfer.models.azure.StorageEntity dst_ase: dst storage entity
          :rtype: str
          :return: unique transfer id
          """
          return ';'.join(
              (src_ase._client.primary_endpoint, src_ase.path,
               dst_ase._client.primary_endpoint, dst_ase.path)
          )